Electric musical instrument



May 10, 1949. E. M. SPIELMAN ELECTRIC MUSICAL INSTRUMENT Filed March 14, 1944 4 Sheets-Sheet l INVENTOR. 'EMER/G M SP/EL MAI! 4 TTORNEY y 1949- v E. M. SPIELMAN 2,469,850

ELECTRIC MUSICAL INSTRUMENT Filed March 14, 1944 4 Sheets-Sheet 2 INVENTOR. EMER/O M. SP/ELMA/V A r TOR/YE Y y 1949. E. M. SPIELMAN T 2,469,850

ELECTRIC MUSICAL INSTRUMENT Filed March 14, 1944 4 Sheets-Sheet 3 CONTACT BAR 55 15 BATTER) INVENTOR. EMER/O M. SP/ELMAN .POS.3 BY

ATTORNEY May 10, 1949.

E. M. SPIELMAN ELECTRIC MUSICAL INSTRUMENT 4 Sheets-Sheet 4 Filed March 14,. 1944 BATTERY Q &b 75 95 Fig-6- INVENTOI. EMER/C M. .SP/EL MAN A TTORNEY Patented May 10, 1949 UNITED STATES PATENT OFFICE ELECTRIC MUSICAL INSTRUMENT Emeric M. 'Spielman,-New York, N. Y.

Application March 14, 1944, Serial No.-526,408

1 Claim.

The present invention consists in improvements .and new devices ,for electric musical instruments which produce tone frequencies by rotating members, particularly of the type described in my former U. 8. Patent No. 1,778,374.

The inventionconsists in a device for execution of accen by models.

The invention iurther consists in a modification and new application of a devicedescribed in my UMS. Patent ,No. 1,977,095,111 order to produce orchestral effect.

I have to interpret the meaning of orchestral effect. We speak of orchestral effect when a band of performers .01 various instruments executes polyphonnlls music. The resulting sound appears as a mixture of voices, each played in different tone colors. The mixture of difierent tone colors, alone doesnot exhaust the characteristic of orchestral effect; it is indispensable that each voice within the mixture sounds with independent accents, dynamically varying. Therefore, We contrast music of an organ which performs upon several keyboards an accentless 'mixture of different tone colors to orchestra music with its matchless abundance of accents. According to these considerations akeyboard instrument ,will produce orchestral effect if it is furnished with means which unitethe possibility .of performing accentuated music and variable :mixtureof tone colors. From the standpoint of musical progre s it is .clearthat a keyboard i strument which fulfills these conditions cannot have the task of imitating or vreplacing an or- .chestra; besides, a better substitute of an orchestra than a record player with power amplifier cannotbe imagined. But ifsuch an instrument should be used to give the possibility of innova in ancrchestra comp sition by new one colorsin an-adeguate instrumentation chosen by the performer, new avenues for musical per.- ,formance .co.u1d be opened.

The instrumentation of an orchestral work comprises ;-a great number of different instruments which, howevencan be grouped in three .catesoriesenamelystringed, wood wind andbr-ass instruments, each ca eg y h i i Own tinctcharacteristic of sounding. This henomenonisutilizedin-a modification oipiy photo- .electrieinstrument, described on p 3 o .11.

.Patent no. 1,173,314 which could corr sp nd to :the mentioned. conditionsoi producing: orchestral cliect quite "well. But as it uses three keyboards and -req-uires 'more than average skill from its playergit couldnever replace the pianoas a-home instrument. With'respect to this aim the prob- '-lem is to produce orchestral: eiiect upon one single keyboard.

The present -=invention solves this problem i by grouping alltone colors in only two categories,

transparent areas -or apertures.

one category comprising tones rich, the other comprising tones poor in harmonics.

The first category represents the sound of stringed and brass, the second category thesound of wood wind instruments; the mixture of both categories is analogous to full orchestra, The division of tone colors in only two categories makes it possible to apply the method of tone color variation, described in my :U. S. Patent No. 1,977,095 in combination with the instrument described in my U, S. Patent No. 1,778,374;. Upon this combination the present device for producing orchestral effects on one keyboard is based.

Theinvention also consists in a device which gives the possibility to play in bass and treble of h m ey o d simu a eo s di e en timbres.

The invention also consists of a device which nabl s th p a r to pply a m tho o pe fo mns si ulta eousl a undefine num o voi es.

Other objects of my invention will be apparent from the following description and the accompanying drawings in which:

Fi 1 is a d as mm i Vi w of e auraratus producing photo-electric current of tone frequency in changeable timbre,

Fig. ZshOWs different types of tone discs, 3 llustr test arrangemen of fla h li ht bulbs-used for pr ducin the same note in seven octaves,

Fig. 4 is adiagram of theflnfih lishtbulbcir .cuit,

Fig. 5 shows one of the screens for varying the tone colors,

Fig. ,6 is a diagramoi thephotocell circuithand i .7 is an utside .View; of the inst ument.

In order to,more.clearlydemonstrate the mam n r of workin of he instant mpr vements and 1 new devices I ,am goingto delineate the entire inmeans of a transmission :to a shaft 2 on which w v pulleys 31-64 m? arran ed, only six bein shown in the drawin Ea h of thesepu eyswrotates y means. of bol s neof twelve pul eys de qu l di m r, each be n a ranged on senarately bedded shaft The peed of the pu leys depends on the different diameters of th pu leys 3 -3 the dimensions of which increase in the same ratio-asthe frequencies of twelve consecu- :Oneach of the pulleys 4 twoopaque circular tone discs are fixed. These discs- 5 and];ihaye'inlannular zones'the same number of regularly distributed Between the discs 5 and 6 light bulbs 30 are arranged in a row. Opposite at the other side of each disc photo-cells 8 are placed. Light beams coming from the light bulbs strike the photo-cells after having passed through the apertures of the discs. When the discs rotate, the light beams become intermittent with a frequency which corresponds to the number of apertures crossing the way of the light beams per second. In the same sequence as light and darkness changes on the photo-cells 8 their electric resistance varies. If these variations follow in tone frequency the photo-cells will produce a fluctuating current of tone frequency which may be made audible on a phone or a loud speaker. The discs 5 and 6, preferably made of transparent acetate sheets, are made opaque by printing thereon light impervious areas, as illustrated in Fig. 2. In this manner seven concentric rings of transparent areas or apertures are created, the innermost ring having two transparent apertures, the second ring four, the third ring eight, the fourth ring sixteen, the fifth ring thirty two apertures, following the rule that the larger ring has always double the number of apertures appearing on the preceding one.

Accordingly, the intermittences of light produced by the same rotating disc have the ratio 1:224:8z16, which is the same ratio the frequencies of the same note have in five consecutive octaves. given more than double the number of apertures following the rule that the number of apertures increases from the innermost to the outermost zone according to the ratio 1 :2 in the inner zones, in the ratio 122.1 in the outer zones. for this deviation is to correct the sounding of the higher octaves according to the sensibility of human hearing which demands the higher octaves to be sharp. As each couple of tone discs synchronously rotating produces the same note in seven consecutive octaves and 12 couples or units are provided, each producing another note within an octave, the tone discs produce eighty four different intermittences corresponding to the tone frequencies of the notes of a chromatic scale covering seven octaves from c to 22 The number and distribution of the tone areas are on both discs 5 and 6 alike, but the shape is different. The apertures on disc 5 are chosen for producing sound poor in harmonics analogous to wood wind instruments, the apertures on disc 6 are chosen for producing sound rich in harmonics analogous to stringed and brass instruments. As indicated in the preamble in this way orchestral effect may be obtained. known shapes are adapted to fulfill the requirements of producing sound containing more or less harmonics, particularly when the apertures are scanned by beams of light optically formed into a light line, a device which is fundamentally used in sound motion picture machines. But an adequate result can also be accomplished by less complicated means. Fig. 2 shows apertures on disc 5 resembling sine waves recorded by an oscillograph and apertures on disc 6 in shape of straight lines; both shapes are specifically appropriate for creating one of the mentioned timbres.

Eighty four light bulbs are arranged in groups of seven between the discs 5 and 6. Fig. 3 and Fig. 5 illustrate this arrangement. A strip 48 suitably fixed to the apparatus holds eight jacks. The bulb carrier 7 is provided with eight plugs seven of the plugs 24 being attached to bulb sockets to fit into the mentioned jacks; one plug 25 However, the sixth and seventh ring is The reason Many variations of one group of bulbs.

is connected with the input of the bulb current and one pole of the above mentioned seven bulb sockets, whereas the other pole of the sockets transmits the output of the bulb current over the plugs 24. The distance between the plugs 24 is equal to the width of the rings on the tone discs; therefore, each bulb is coordinated to one ring, the same in both discs 5 and 6. In order to facilitate the replacement of bulbs, the carrier 1 is removable by means of a handle 26 which can be pivoted around the screw I21.

Placed under the handle 26 a combination of screens is provided; Fig. 3 shows them removed. The opaque strip 21 supports a row of screens 29; each of them separates optically two adjacent bulbs. Strip 2! contains seven holes 28. Passing through these holes the beams of light, directed to disc 5, form light spots on the rings, each spot not larger than one ring; therefore, the light of each bulb passes through the apertures of only one ring, namely the opposite ring. On the other side of strip 21 the screens allow the beams of light to form light spots larger than the rings; therefore, the light of one bulb passes not only through the apertures of the opposite ring, but partly also through those of the next two rings. In this case not only the note of the opposite ring, but also the same note in the next higher and lower octaves will be audible in consonance; in this way the disc 5 also is supported in its destination of creating sound with numerous harmonics.

The light of each bulb strikes both discs 5 and 6 simultaneously; therefore, a mixture of the timbres produced by the tone discs is heard. In order to make audible either the timbre of disc 5 or that of disc 6 the simplest way is to cover the disc of the not demanded timbre by a movable opaque screen. This procedure is utilized in a device which makes it possible to play on the same keyboard in bass and treble different timbres simultaneously.

For this purpose a bar In, Fig. 1, is provided parallel to shaft 2 holding twelve specifically shaped screens 9, each placed between disc 5 and By means of a pedal II all screens are movable together vertically up and down.

In Fig. 5 one of the screens is to be seen in its normal position which allows the light passing to the disc 6 indicated in the drawing by the site of the filaments. This is the position for playing full orchestra. The pedal H is connected with a suitable mechanism which makes it possible to turn and hold the screens 9 in two other positions shown in Fig. 5. In the position II, following the normal position I, the part M of the screens covers the four rings of the disc 6 which produce the notes of the four bass octaves; in the position III the part N covers the three rings of the disc 6 which produce the notes of the three treble octaves. Therefore, when the screens are turned to position II all notes of the four bass octaves will sound in the timbre of disc 5 analogous to wood wind instruments and simultaneously all notes of the treble octaves analogous to full orchestra. In position III the bass will sound analogous to full orchestra and the treble analogous to wood wind instruments. Other combinations of timbres, different in bass and treble, can be made, using on the same bar l0 another row of twelve similarly shaped screens between the bulbs and disc 5. But all devices based on the method which uses screens for varying tone colors have the same deficiency; they change tone colors only in steps and not continuously. The continuous passing from one timbre to another within one and the same note contributes very much to the art of musical expression. A singer possesses this timbre changeability by passing from chest register to head register; a Violinist can alter the timbre by using the bow either on its lower end or on the point.

Fig. 6 shows a diagram of the photo-cell circuit and the means by which continuous variation of tone color can be accomplished. The battery 59 provides direct current to the photo-cells 8 by two circuits each of them including in parallel twelve photo-cells either on the side of disc 5 or disc 6. The drawing Fig. 6 shows only one cell of each group So and 82). Each circuit leads to one of the split primary windings of a transformer 60. The secondaries of this transformer are center tapped; each half of the secondaries is shunted by one of the potentiometers 63 the rotating arms of which are secured to two toothed wheels 62. Both wheels can be moved together by a driving chain 64, one link of which is attached to a frame 65 which is adapted to glide horizontally along a rail 66. Thisrail is fastened underneath the keyboard and placed in a manner that the gliding of the frame can be accomplished by the left knee of the player, moving the knee from left to right or vice versa. Fig. 7 shows the frame in connection with the keyboard. The secondary windings of the transformer 60 are connected with the primary windings of transformer 6| the secondaries of which lead to the input terminals of the amplifier H. The currents produced by the photo-cells 8a and 8b flow through the primaries of the same transformer (it; there- L fore, its secondaries deliver a mixture of both. It is possible gradually to check the flow of one of the currents by turning the arms of the potentiometers, whereby only the other will be audible.

The frame 65 is seen in Fig. 8 in a position in which the rotating arm of one potentiometer 63 short-circuits the shunt pertaining to the circuit of photo-cell 8a while the arm of the other potentiometer provided maximum value of resistance of the shunt pertaining to the circuit of photo-cell 8b. In this position of the frame only tones rich in harmonics will be sounded. When it is moved to a middle position a mixture of both timbres, and tea position at the right end-of the rail tones poor in harmonics will be heard in continuous passing from one timbre to another.

The described method of shunting the photocell currents improves the method described in U. S. Patent No. 1,977,095 by the arrangement of only one transformer in order to enhance the mixture of timbres and by the use of a gliding frame which can be handled by the knee easier than by a pivoted lever.

Uniform speed of the motor is essential for the invariability of the produced tone frequencies. Although the ratio of tone frequencies is secured by the ratio of the pulleys 3 -3 once for all the pitch of the notes depends upon a strictly defined speed of the shaft 2. In order to secure an equal constant speed it is advisable to employ a synchronous brushless induction motor, but in this case the instrument can be exclusively used on A. 0. current.

In order to make the instrument playable on A. C. or D. C. current an universal motor maybe provided the speed of which is controllable by a power 'rheostat. Within certain limits the speed of any brush motor can be adjustedby applying a brake. In accordance with this method a brake device is fixed on shaft 2. A brake disc 12 is "fastened to the fixed .ring 43. by meansof flexible steel tapes 45. When rotating the weights '4'4ca-ttached at the tapes rotation of the weights contracts the tapes because of the acting centrifugal force in this way passing the brake'disc l2 gliding on shaft 2 against brake block '42. By means of the screw 82 the. pressure of the block can be adjusted and in this way .a precise number of revolutions per second obtainedand maintained. The correct number of revolutions .is adjusted when the discs fixed to pulley 3. produce the note c in standard pitch. The described brake device makes it possible to transpose the whole scale by turning the screw .82. The correct adjustment of a chosen pitch, respectively of a chosen number of revolutions per second is indicated by the pointer 20 of a speedometer "l8 connected with shaft 2 bymeans of a flexible shaft H. The dial of the speedometer (tachometer) 1:8 is not marked to gauge the number of miles or revolutions but to indicate the speed necessary to create certain pitches. It shows several marks; a red one indicates the speed necessary to produce the note c in standard pitch by depressing the .0 keys and some black marks indicate transposition two half tones higher or lower. .In order to signify a mark for a pitch which should be chosen deviating from the standard pitch an adjustable pointer is fixed on the outside of the glass covering thedial. The instrument will. play in standard pitch when the pointer of the speedometer-coincides with the red mark on the dial.

The quality of the tones producedphoto-electrically by rotating members is modifiable by the means which transmit the rotation. When the belts transmitting the rotation of the pulleys 3 -3 to the pulleys 4 are made endless and of cotton, leather or another nonelastic material the produced tones are not sweet and euphonic enough. To eliminate this deficiency the belts employed in the improved instrument are composed of a longer portion of nonelastic material and a shorter portion of elastic material. These portions are connected to form aniendless belt either by sewing them together or preferably by hooks and eyes. By this combination the speed of the pulleysll is rendered variable, that is slower or faster within very narrow limits, making the quality of tones resembling to tones of stringed instruments when the player rocks his finger on the string, in this way altering the length of the string within very narrow limits. The described combination belts produce analogous tiny fluctuations of frequency in this way creating tones full of life and euphony.

II. K eyboard and action Each of theeighty-four light bulbs is assigned to one key of a keyboard comprising seven octaves. The pressure of a key transferred to a special mechanism, i. e. action, effects .not only switching on the light, but also increases and decreases the light intensity according to the depth of the key pressure. In the improved instrument fundamentally the construction of the keyboard and action is the same as described in U. S. Patent No. 1,778,374.

III. Circuits In Fig. 4 the circuit of one bulb is to be eel nected with the'input of 117 volt A. C. in order to eliminate photo-electric pick-up of the 11; ie of the A. C. input the bulbs must carry .iered direct current. Therefore, a filamenttrairfcrmer 49 is provided'which.delivers.A..C. current of suitable voltage toa metal rectifier ifl, the D. C. cur

rent of which charges a storage battery The battery serves as voltage regulator and hum filter. The minus terminal of the battery is connected with the jack on strip 48 which the plug 25. This plug is the common pole of the seven bulb sockets arranged on carrier 1. On the storage battery 5| two plus terminals are provided, one for the full output of the battery voltage, the other for an output of a lower voltage resulting by omitting the last battery cell, 1.2 volt less using an Edison battery. These two terminals are connected with a two circuit push switch 89 which can be acted on by a lever 90, Fig. 7, for a purpose explained hereinafter. Normally the terminal of the lower voltage is switched on so the battery current passes from this terminal over the lead 75' through the rotating interrupter I3 to the lead and from there over one or both of two two-way switches to one or both bars and 30. Each of these bars, insulated from each other, bears forty two spring tapes I28. When the corresponding key is pressed down, the bulb attached to the socket 24 in Fig. 5 receives periodically interrupted current, effecting tremolo. By means of the switches 52 and their bilateral connection with t and t it is possible to short-circuit the interrupting process either in the circuit leading to the bar 30 or the bar 30. In this way tremolo can be made audible either on the side of bar 30', i. e. bass or on the side of bar 30, i. e. treble, or on both sides according to the chosen position of the switches 52.

When the adjustment of the contact 3! coincides with the extreme point which the spring tape I28 by rolling on the resistor may reach, the full voltage of the connected plus terminal of the battery reaches a bulb. It is obvious that all notes of the keyboard must sound at the same strength when the keys are fully pressed down.

But for this purpose it is ineffective to adjust the contacts 31 of all notes alike at the mentioned extreme point, because on the one hand eighty four light bulbs usually have different effectiveness of light emission so producing at the same voltage tones of not exactly the same loudness; on the other hand, twenty four photo-cells of exactly the same sensitivity are difiicult to manufacture. In order to compensate the dfferent effectiveness of bulbs and photocells the voltage set at the bulbs exceeds the normal voltage the bulbs are built for. The voltage surplus is reduced separately for each bulb by a fixed resistor 35 and an additional variable resistance resulting by adjusting the contact 31 beyond the extreme point which the spring tape I28 touches on the resistor 35. By choosing the right value of the additional resistance the maximal tone intensity according to the deepest key position can be equalized. By this procedure to be controlled by the ear automatically equal strength of intermediate tone intensities are secured because the resistors 35 are all of the same value.

Performing crescendo and decrescendo extended over a musical phrase may be obtained by using a variable resistor parallel to the input terminals of an amplifier.

The whole tone character of the instrument can be made darker and softer by connecting a condenser 69 parallel to the primaries of the input transformer GI and closing the switch iii. In order to make the tone character lighter and sharper, the secondaries of a transformer T5 are arranged in series with one of the secondary windings of an intermediate transformer 13 provided between any consecutive stages within amplifier II. This effect can be altered by changing the impedance of the transformer 16 for this purpose the primaries of this transformer are connected parallel to a variable condenser adjustable by the knob 18, see Fig. '7. When the switch 11 is closed, this device becomes ineffective.

IV. Pedals Fig. 7 shows the exterior view of the instrument and the arrangement of the pedals.

There are four pedals 80, ll, 55 and I19 provided to be trodden by the foot, and two devices 65 and operated by the left and the right knee of the player. The mode of operation of the frame 65 and the pedals 80, H and H9 has been previously described. The lever 90 and the pedal 55 make it possible to perform siorzando. The lever 90, when pressed upward by the knee, controls the switch 89, Fig. 5, in a way that the lead it becomes connected with the battery terminal of the higher voltage. Swift input of higher voltage effects suddenly increased intensity of light respectively suddenly increased loudness, i. e. accent. This sforzando becomes particularly impressive when the lever 90 is moved while keys are fully pressed down, so the resistance in the bulb circuit is a minimum, because then the overcharged filaments have the greatest light emissivity. overcharging the filaments diminishes the lifetime of bulbs. But as it is possible nowadays to manufacture bulbs enduring 25% voltage increase overcharging has lost a great deal of its injuriousness.

W'hile by the described device fortissimo sforzando can be executed within forte played passages, the pedal 55 makes it possible to perform forte accents within piano or mezzoforte played passages. By the same pedal an effect may be created.

The constructional principle of the pedal 55 is apparent from Fig. 4. The treadle 55 bears on its underside two metal strips 56 and 51, insulated from each other. These strips form a normally closed contact in the circuit mi. The treadle can be operated in two steps. On the deeper step the knob 58 touches the floor and breaks the contact. The circuit nn' comprises a resistor 58 shunting the windings of the volume control 68, i. e. the input of the amplifier. Therefore, when the pedal 55 is moved two steps down, the parallel resistance 68 disappears and the instrument sounds suddenly louder in every position of the volume control.

The other side of the treadle 55 is connected by a rod with a normally open switch 54 which controls the circuit II when the switch 53 is closed. The circuit H carries current for the bulb l5, Fig. 1. Opposite this bulb a photo-cell i6 is arranged which, receiving current by the circuit dd, Fig. 6, lies in the circuit of the input transformer 5|. Between bulb l5 and photocell IS a tone disc [4, Fig. 2, is fixed on the same shaft which bears the rotating interruptor 13. The apertures of the tone disc M are shaped for producing sound resembling drumbeats; therefore, when the pedal 55 is trodden halfway, while switch 53 is closed, drum sound will be audible either as accent or roll. The switch 54 is necessary in order to make the pedal 55 usable for two purposes.

Fig. 2 shows a tone disc l4 with 4 concentric zones each of which is provided with photographic registration of the sound of another percussion instrument. The disc is arranged between a photocell and a carrier of 4 bulbs l5 -l 5" 9 one opposite of each ring. By means of switches s -s which connect each of the bulbs with the bulb current it becomes possible to turn on the light bulbs singly or together by the same pedal.

V. Assemblage The case of the instrument 9|, Fig. 7, is horizontally divided by a shelf the position of which is illustrated by the dotted lines 92. The upper compartment holds the apparatus, the lower con tains the amplifiers, the speaker and the battery. The shelf 81 and the keyboard lid 99 are removable so the action becomes fully visible for adjustment, if necessary. The ammeter 8i indicates the charging condition of the battery. Beside the screw 82 which controls the speed of the motor the speedometer I8 is situated; 33, 6t, and 86 designate the switches of motor, rectifier, amplifier and photo-cell battery; 72 and 12 are volume controls acting on the input and output of the amplifier. 93 is an outlet box connected with the input of the amplifier over the switch 96; is an outlet box connected with the output of the amplifier over the switch 96. These two outlets constitute the device which enables the player to apply a method of performing simultaneously an undefined number of voices.

The scores of orchestral works mostly comprise a large number of voices; therefore, piano trail" scriptions of these works must be arranged for two players to render the entire polyphony au dible. The hereinafter described method enables one player alone to perform piano music arranged for two players simultaneously on the same keyboard.

The method consists in the following procedure which is applicable also in combination with nonelectrioal musical instruments. The player plays first one part of the voices of a composition, at the same time making a record of his playing on a recording unit; then he plays the other of the voices together with the recorded one; two fundamental conditions must be fulfilled to secure the effectiveness of this method; first the number of rotations per minute of the turntable must constantly be the same, secondly the instrument must have constantly the same pitch or must be tuneable to a predetermined pitch, which has to be exactly equal while the two parts are played. For instance, a violinist who wants to play a concerto written for two violins can successfully apply the method using a recording unit which mostly will suit the first condition because such units are chiefly equipped with brushless induction motors and devices which secure the standard speed of 78 R. P. M. He has only to pay full attention to the pitch of his violin which has to be exactly the same when he plays the first and the second part of the composition, otherwise difference of pitch when playing together with the record becomes inevitable.

The method applied in combination with nonelectric instruments has the disadvantage that the recorded part becomes audible on a loudspeaker, so the quality of its sounding does not perfectly match that of the other part. When used in combination with electric musical instruments this disadvantage disappears because both parts sound on the same loudspeaker in thorough blending.

The two mentioned outlets 93 and 95 make possible the connection of the recording unit with the instrument; 93 connects the play-back with the input, preferably the second stage of the amplifier, because sound reproduction by a phonograph does not require the full amplification photo-cells require. Outlet connects the cutting head with the output of the amplifier, which preferably is provided with a universal output transformer to match the impedance of different types of cutting heads.

t will be understood by those skilled in the art that modifications of my present invention, applicable to non photo-electric instruments can be made without departing from the spirit of this invention or the scope of the subioined claim. I, therefore, claim as my invention modifications whereby substantially the same effect may be obtained in a substantially analogue way.

I claim:

An electric musical instrument for the performance of multivoiced music with orchestral effect comprising twenty four tone discs having transparent areas regularly arranged in concentric annular zones, the number of which increases from the innermost of the outermost zone according to the ratio 1:2 in the inner zones, in the ratio 122.1 in the outer zones, the said twenty four tone discs arranged in twelve groups of tone disc couples, the transparent area of one tone disc of each couple shaped to produce tone frequencies having a timbre poor in harmonics, the transparent areas of the other tone disc of the couple shaped to produce the same tone frequencies having a timbre rich in harmonics, a plurality of light bulbs and photo cells situated in combination with the tone disc couples to produce each note in a mixture of said two timbres, means to adjust the relation of harmonic poor and harmonic rich tone frequencies within the mixture, a key board, means to control the intensity of the light of each bulb according to the depth the coordinated key is depressed, a motor, means to rotate the twelve groups of tone disc couples with different speed increasing in the same ratio as the tone frequencies of twelve consecutive notes increase within an octave, means to control the speed of the motor, a speedometer indicating the pitch, current supply for the light bulbs, current supply for the photocells, an amplifier, a resistance shunting the input of said amplifier and a pedal to disconnect said shunt, two outlets one of which connected with the input, the other connected with the output of said amplifier, and a speaker.

EMERIC M. SPIELMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 194,993 Crossley Sept. 11, 1877 393,902 Heffner Dec. 4, 1688 393,966 Edison Dec. 4, 1888 1,848,222 Potter Mar. 8, 1932 1,836,687 Jacobs Nov. 8, 1932 1,948,996 Toulon Feb. 27, 1934 2,014,741 Lesti Sept. 17, 1935 2,030,248 Eremeeff Feb. 11, 1936 2,031,764 Eremeeff Feb. 25, 1936 2,073,812 Severy Mar. 16, 1937 2,161,706 Hammond June 6, 1939 2,169,842 Kannenberg Aug. 15, 1939 2,184,424 Hammon Dec. 26, 1939 2,301,871 Hancrt Nov. 10, 1942 

